The present invention relates generally to semiconductor manufacturing processes and equipment, and more particularly to methods and systems for detecting units in an output track of semiconductor test equipment and for safely removing semiconductor storage tubes therefrom.
Semiconductor devices are typically constructed in large quantities on a wafer of silicon. Such devices include an integrated circuit (IC) die, which is mounted onto the die-mounting pad of a leadframe. Wire attachment pads on the die are then connected with corresponding leads on the leadframe, typically with aluminum or gold wire during a wire bonding process. The die and leadframe are then encapsulated in a plastic or ceramic package, thus yielding an IC xe2x80x9cchipxe2x80x9d semiconductor device. During the manufacturing and testing of such devices, the chips are commonly stored in protective containers, such as a plastic tube with plugs at both ends to prevent the chips from falling out of the tube during handling or shipment.
Semiconductor devices, including integrated circuits are stored in plastic tubes to protect the devices, and particularly the leads thereof, in order to prevent damage such as bending and breaking. In addition to providing for storage ease and mechanical protection for the semiconductor devices, the storage tubes also provide protection against electrostatic discharge (ESD) by the use of appropriate materials in the construction of the tubes. Certain types of storage tubes have a platform or rib extending longitudinally through the center of the tube on which the body of the device is supported with the conductor leads on each side of the device separated by the platform.
Each end of the tube may include vertically oriented holes through which a resilient pin type plug may be inserted to extend through the tube, in order to prevent the devices from falling out of the tube. Alternatively, or in combination, soft foam type rectangular plugs may be inserted into one or both longitudinal ends of the tube to ensure against devices exiting the tube during handling. Since the plug needs to remain in the storage tube without falling out, the end of the pin type plugs may be slightly enlarged to hold the plug in the end of the tube and remain there until forcibly removed. The foam type plugs generally remain inserted in the tube ends via a frictional interference fit. In addition to the vertical holes located near the ends of the tube, additional holes may be provided in the storage tube whereby semiconductor devices may be further inhibited from sliding longitudinally between the tube ends by the insertion of additional pin type plugs therein, for example, where the tube is only partially filled with chips.
Such tubes may accommodate various types of integrated circuit chips having a variety of lead patterns and types. For example, thru-hole devices may be stored in such tubes, as well as surface mount type devices having various lead configurations (e.g., xe2x80x9cjxe2x80x9d type, xe2x80x9cgull wingxe2x80x9d type, and other type leads). In addition, the storage tubes may accommodate chips having leads on two opposite sides as well as those having leads on four sides. IC chips come in a variety of forms, such as microprocessors, dynamic random access memory (DRAM) chips, static random access memory (SRAM) chips, flash memory chips, gate arrays, etc, all of which may be stored in such semiconductor device storage tubes.
In the manufacture of semiconductor devices, the parts are typically tested prior to insertion into the storage tubes. Typically, the testing of the devices, as well as the insertion thereof into the storage tubes after testing, is done using automated test equipment or systems. Where one or more performance measures or characteristics of the tested devices is of concern (e.g., memory access time, processor or other logic device speed, A/D converter resolution), the test equipment may sort the tested devices according to such performance measure or measures. In other types of device testing, physical characteristics of the parts (e.g., coplanarity, lead spacing footprint, xe2x80x9ctweezexe2x80x9d or outside lead dimensions, etc.) may be tested. For example, lead inspection stations provide for measurement of such dimensional attributes or characteristics associated with semiconductor chips. Tested semiconductor devices are sorted by the tester into groups of parts having similar tested performance and/or physical characteristics, and stored into storage tubes according to the sorting.
Semiconductor device testing is typically accomplished using automated testers having automatic device loading and unloading mechanisms located respectively at the input and output of the tester. Devices under test (DUTs) are loaded into the tester, and tested for one or more performance and/or physical characteristics. The tested devices are then sorted according to the test results and provided to an output stage of the tester or inspection station. The output stage may include one or more device output tracks in which the tested parts travel to storage tubes receiving the devices from the output track. Automatic tube replacement devices remove filled storage tubes and provide empty storage tubes to receive devices from the output tracks. In the past, the tube replacement devices were operated according to control signals from a programmable logic controller (PLC) or other type of controller, which actuated the replacement of filled tubes with empty tubes according to a sensor detecting whether the tubes were filled.
However, as the filled device storage tubes are removed, devices remaining in the output track may become jammed or otherwise be damaged. For example, a semiconductor device chip may be partially inserted in the entrance end of a storage tube or otherwise be near the tube when the tube replacement device removes the storage tube. Such devices in the output track may be jammed between the moving storage tube and adjacent components in the tester output stage, and device damage may result. In addition, devices partially inserted into the storage tube may become dislodged therefrom and fall during movement of the tube by the tube replacement device, in which case the device may also become damaged. Such damage to tested semiconductor devices at the output stage of a tester decreases the effective yield of the manufacturing process, and hence is costly. Thus, there is a need for methods and systems by which such device damage is reduced or eliminated.
The following presents a simplified summary of the invention in order to provide a basic understanding of one or more aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention, nor to delineate the scope of the present invention. Rather, the sole purpose of this summary is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented hereinafter. The present invention provides systems and methods for testing semiconductor devices, using a tester providing tested semiconductor devices to a device output track, which feeds the semiconductor devices into a storage tube.
According to an aspect of the invention, the tester selectively removes the storage tube from the output track when the tube is filled and when no device is in the output track proximate the semiconductor storage tube. In addition, the tester refrains from removing the storage tube from the output track when a semiconductor device is in the device output track proximate the storage tube, so as to prevent or reduce damage to semiconductor devices during removal of the storage tube from the output track.
The test system may comprise a first sensor to detect whether the storage tube is filled with semiconductor devices and a second sensor to detect whether a semiconductor device is in the device output track proximate the semiconductor storage tube, wherein the second sensor may comprise a fiber optic sensor and an amplifier. In this case, the tester selectively removes the semiconductor storage tube from the output track when the first sensor indicates that the storage tube is filled and the second sensor indicates that no device is in the device output track proximate the storage tube, and refrains from removing the storage tube from the output track when the second signal indicates that a device is in the output track proximate the storage tube. The tester may also generate an alarm when the storage tube is filled with devices and when a semiconductor device is in the output track proximate the storage tube.
Another aspect of the invention provides a method of operating a semiconductor device tester, comprising providing semiconductor devices to a device output track associated with the tester and feeding semiconductor devices along the device output track into a semiconductor storage tube associated with the device output track. The method further comprises selectively removing the storage tube from the output track when the storage tube is filled and when no device is in the output track proximate the semiconductor storage tube, and refraining from removing the storage tube when a semiconductor device is in the output track proximate the tube, whereby damage to semiconductor devices during removal of the semiconductor storage tube from the device output track is reduced or prevented.
To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative aspects and implementations of the invention. These are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other aspects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.